[Problem] During hybrid propulsion of a ship, to assist a motor using an assist torque command value obtained by PID calculation of the deviation between a present value and a target value for main engine output and to efficiently operate a governor-controlled main engine. [Solution] A ship propulsion device 1 that has: a propeller 9; a main engine 2 that is controlled by a governor 3; a motor 14 that has torque control performed thereon by an inverter 12; and a controller 4. A PID regulator 25 of the controller controls the inverter using an assist torque command value obtained by PID calculation of the deviation between a present value and a target value for main engine output, and, as a result, distribution of main engine output and motor assist amount can be optimized, and the governor-controlled main engine can be efficiently operated.